Tackling postoperative sudden cardiac death in high-risk cardiac surgical patients—role of wearable cardioverter defibrillators

A specific analysis of patients from the STICH trial (Surgical Treatment of Ischaemic Heart Failure) revealed that the risk of sudden cardiac death (SCD) in coronary artery bypass graft surgery patients with severely impaired left ventricular (LV) function is highest between the first and third month postoperatively [1]. According to current guidelines, the indication for permanent implantable cardioverter defibrillator (ICD) therapy should be evaluated 90 days post-revascularization and bridging this time period with a wearable cardioverter defibrillator (WCD) may be reasonable [2]. The reported study results of Kuehn et al. [3] in this issue of the journal support the importance of early postoperative WCD bridging in cardiac surgical patients with severely impaired LV function to reduce or eliminate the risk of SCD. In total, 9.1% of 1168 patients had at least one episode of ventricular arrhythmia while wearing the WCD and 1.5% received an adequate and effective shock. No ineffective therapy occurred and the inadequate shock rate was low at 0.7%. The overall study cohort is inhomogeneous and to fully comprehend the findings of this study, it is important to separate patients with ischaemic and/or valvular cardiomyopathy from the ICD explant group. Patients after ICD explantation are obviously at high risk for ventricular arrhythmias, since this was the initial reason for ICD implantation and it is common sense that they will benefit from temporary WCD bridging until permanent ICD reimplantation. More interesting are the results of the subgroups of cardiac surgical patients with ischaemic and/or valvular cardiomyopathy. The results confirm the existence of an SCD risk in the early postoperative period of such patients and prove the efficacy as well as safety of WCD bridging to reduce/eliminate this risk. Besides, it is important to understand that another beneficial effect of WCD bridging is to avoid unnecessary ICD implants in cases of myocardial recovery and improvement of LV function, which translates into reduced morbidity and mortality as well as economical benefits. Beyond LV-ejection fraction (EF) description, the coronary artery bypass graft surgery cohort was poorly defined in this study. Therefore, unknown variables, such as scar burden, coronary anatomy and completeness of revascularization may have affected myocardial recovery and the reported numerical effect of LV-EF improvement may even be more pronounced in certain favourable patient groups. The results of this study should be interpreted under the limitations of a retrospective study, but certainly underline the benefit of early postoperative WCD bridging in cardiac surgical patients to reduce SCD until final evaluation for permanent ICD implantation. As the first large study solely focusing on the cardiac surgery cohort, the findings provide a novel database for the development of indications for WCD use in cardiac surgery as proposed by a working group of the DGTHG (German Society for Thoracic and Cardiovascular Surgery) in 2018 [4]. The use of WCDs should become a standard-of-care in cardiac surgery to reduce early postoperative SCDs in high-risk patients and to avoid the detrimental medical as well as economical effects of unnecessary ICD implants. A prospective registry or trial is needed to confirm the results and to further define the patient population at risk. Conflict of interest: C.S. declares payment to his institution related to his activity as speaker fees, honoraria, consultancy, advisory board fees, investigator, committee member from Angiodynamics, Abiomed, Medtronic, Spectranetics, Biotronik, Liva Nova (Sorin) and Cook Medical and departmental or institutional research funding from Cook Medical. V.F. declares relevant (institutional) financial activities outside the submitted work with following commercial entities: Medtronic, Biotronik, Abbott, Boston Scientific, Edwards Lifesciences, Berlin Heart, Novartis Pharma, JOTEC/Cryolife, LivaNova, Zurich Heart in relation to educational grants (including travel support), fees for lectures and speeches, fees for professional consultation, research and study funds. J.K. declares no conflict of interests.